Background. Chlamydia trachomatis is the most common sexually transmitted bacterial infection in the United States, with 3 to 4 million cases occurring annually. Most cases occur in those less than 25 years old. Increased prevalence has been found in patients who live in inner cities, have a lower socioeconomic status, or are black. Up to 80 percent of women infected with Chlamydia are asymptomatic and do not seek medical care. In addition to Pelvic Inflammatory Disease (PID) and its sequelae, chlamydial infections also may facilitate acquisition of HIV. Treatment is simple, effective, and cost effective. Despite recommendations by the Centers for Disease Control and Prevention, most high-risk women are not being screened. The UAB Center for Outcomes and Effectiveness Research and Education, in collaboration with U.S. Quality Algorithms, the performance measurement subsidiary of Aetna U.S. Healthcare, proposes a controlled, group-randomized trial to increase adherence to guidelines for chlamydial screening in at-risk women. Specific Aims. (1) to increase rates of chlamydial screening for at-risk female patients; (2) to increase rates of treatment for Chlamydia; and (3) to decrease the incidence of PID. Methods. We will randomize 220 primary care physician offices and their at- risk female patients to either an intervention or control arm. Patient risk status will be defined by the specifications of HEDIS 2000. Our intervention consists of a year-long series of physician Internet learning modules that integrate case-based education with audit, feedback, and benchmarking of practice profiles. Analysis. The major comparison will be the differential improvement in screening rates of the two study arms as ascertained from administrative data. Patient-level multivariable analyses will adjust for the extra-binomial variation resulting from patients being nested within physicians from the group randomized design. Significance. With a research team that has a proven record of collaboration, this project will produce an evidence-based and replicable intervention than can be sustained in the "real world," readily adapted by other health care organizations, and easily modified for other diseases.